1. Field of the Invention
The present invention relates to communication apparatuses connecting between a terminal and a network by wireless, and more particularly to a communication apparatus, an IP address acquisition method and a roaming method in which the terminal can acquire an IP address from an addressing server.
2. Description of the Related Art
In order to communicate by using IP (Internet Protocol) in a network such as a LAN (Local Area Network), it is necessary to acquire and set an IP address for a terminal. There are two methods to set the IP address for the terminal; One is a method in which the IP address is manually set. The other is a method in which the IP address is set by using DHCP (Dynamic Host Configuration Protocol). When the IP address is manually set, a network administrator needs to manage IP addresses for terminals therein so that an identical IP address cannot be simultaneously allocated to a plurality of terminals. In contrast, under the DHCP, an IP address is dynamically and automatically allocated to a terminal. In the DHCP, when a terminal gains access to a DHCP server, an IP address is allocated for the terminal. The DHCP is currently used in a large number of networks.
On the other hand, a wireless LAN has been widespread recently. As shown in FIG. 1, in a wireless LAN, information is communicated by wireless between a station 10 connected with a PC 14 and an access point 12 connected with the LAN. In FIG. 1, the station is connected with the PC 14 by a fixed line, and the access point 12 is connected with a network by a fixed line. Also, a DHCP server 18 is connected with the network.
In such a wireless LAN, IP addresses have to be allocated to not only the PC 14 but also the station 10 and the access point 12 that are serving to implement wireless communication.
A description will be given of a procedure to set an IP address for the PC 14 by using the DHCP server 18 under this configuration. At the beginning, there are prepared the same number of IP addresses as the number of access points. In this configuration, just one IP address should be prepared because there is only one access point 12. Next, a temporary IP address is manually set to the PC 14. As the temporary IP address, there is provided an IP address whose network address (to be mentioned later) is identical to that of the prepared address. After receiving the temporary IP address, the PC 14 is engaged to set the prepared IP address to the station 10 and the access point 12. Since this configuration has just the access point 12 therein, the station 10 and the access point 12 may have an identical IP address. Thus, the identical IP address is allocated to the station 10 and the access point 12.
The station 10 and the access point 12 to which the identical IP address is allocated are connected with the PC 14 and a network 16, respectively. In this manner, the PC 14 gains a connection with the network 16 via the station 10 and the access point 12. After that, an IP address setting of the PC 14 is modified into a setting such that the PC 14 acquires an IP address through DHCP, and then the PC 14 is rebooted to apply the modification. In the above-mentioned procedure, the PC 14 can acquire an IP address from the DHCP server 18 via the station 10 and the access point 12.
As mentioned above, even when the DHCP is used to set an IP address automatically in a wireless LAN, it is necessary to perform complicated tasks for setting some apparatuses to implement a wireless LAN and further reboot a PC to apply a new setting.